Various types of sensing devices have been developed for monitoring a variety of conditions. One of the more important conditions often monitored is that of combustion in an effort to discover and thus minimize loss due to fire, particularly in buildings or other structures where the presence of a fire could go unnoticed until far too late to minimize loss to any appreciable extent.
Combustion detection devices have heretofore been suggested and/or utilized, but such devices have not proved to be completely satisfactory for all situations due to such diverse factors as being subject to mechanical and/or electrical component failure, vacuum leakage and aging where vacuum tube structures are utilized, and/or being relatively complex and/or of expensive construction so as to be impractical for at least some uses.
A combustion detection device providing pulsed sensing utilizing an ionization detector is shown, for example, in U.S. Pat. No. 3,842,409, entitled, "Ionization Detector Apparatus," issued Oct. 15, 1974 to Ronn H. Mayer and assigned to the assignee of the present invention. The detector of this invention constitutes an alternative to the structure shown and claimed in U.S. Pat. No. 3,842,409.
Various fire detection devices are also shown in U.S. Pat. Nos. 3,795,904 and 3,798,625, while a condition responsive door holder-closer utilizing a radioactive source of americium is shown in U.S. Pat. No. 3,777,423.